A single wafer processing apparatus, which processes substrates one by one, is one of systems for performing a semiconductor processing on a substrate to be processed such as a semiconductor wafer. Further, there is a multi chamber type semiconductor processing system, wherein a plurality of such processing apparatuses are coupled to each other via a common transfer chamber such that various processes can be successively executed without exposing a wafer to the atmosphere. Such a semiconductor processing system may include a normal pressure processing type as disclosed in Japanese Patent Laid-open Publication No. 7-86375 and a vacuum processing type as disclosed in Japanese Patent Laid-open Publication No. 2000-195925.
In the system disclosed in Japanese Patent Laid-open Publication No. 7-86375, a plurality of processing chambers are disposed in a line, and at least some of the processing chambers are disposed vertically. A transfer device movable parallel to the processing chambers is disposed in order to transfer a substrate thereto. The transfer device includes a moving base movable on rails. Stood on the moving base is a pair of supports, which is connected to a vertically movable housing via a vertical arm mechanism. Provided in the housing is a horizontal arm mechanism having a substrate supporting unit capable of supporting two substrates.
In the system disclosed in Japanese Patent Laid-open Publication No. 2000-195925, a transfer chamber capable of being depressurized is surrounded by a plurality of vacuum processing chambers and load lock chambers. Processing chambers and load lock chambers are disposed vertically at least one location around the transfer chamber. A transfer device is disposed in the transfer chamber and includes a pair of small-sized arm mechanisms stretchable and contractable horizontally. The small-sized arm mechanisms are disposed such that they can revolve horizontally and move up and down.
Both systems described above are equipped with two substrate supporting units or two small-sized arm mechanisms, but their transfer efficiencies are not no satisfactory.